Figure 2.  The low levels of Qa1 expressed on blast cells are sufficient to protect them from lysis by Qa1R+ NK cells
Aliquots of 5000 L cells, L cells transfected with Qa1 [LQ], normal B6 ConA blasts or cI-deficient
b2m -/- blasts were incubated with graded doses of J1.1 effector NK cells that uniformly express
Qa1 receptors
Conclusions
1.  L cells transfected with Qa1 molecules are protected from lysis by NK cells expressing Qa1R
[but not by Qa1R- NK cells, data not shown]
2.  Despite their apparently low level of Qa1 expression, normal blast cells are also protected from
Qa1R+ effectors
3.  This suggests that only very low levels of Qa1 molecules are required to protect normal cells
from NK cells, due to the fact that normal cells have only weak activatory signals as shown by the
much higher numbers of NK cells required to kill them compared to L cells and tumour cells
4.  Alternatively, the form of the Qa1 molecules recognized by the mAb 4C2 may not be the protective
form